The present invention relates to curable organopolysiloxane compositions. In one aspect, the present invention relates to an improved encapsulating resin.
Organosiloxane resins in which the substituent organic groups are methyl, phenyl, vinyl and/or other organic groups are well known. These resins are cured by a variety of mechanisms, such as by cross-linking through a vinyl group or by the platinum catalyzed reaction of .tbd.SiH groups with alkenyl radicals, to form hard infusible materials. The properties of these organosiloxane resins, such as toughness, high dielectric capacity, resistance to thermal decomposition and retention of strength at high temperatures, make them useful in many different applications.
Certain applications, such as encapsulating electrical components and coating of coils for electric motors, provide a very severe environment for the use of presently available resins. The resins must be strong, yet flexible and must retain their strength under repeated thermal shock. Also, the resin must cure without the evolution of volatiles, such as solvents or water, in order to avoid the formation of bubbles and/or voids in the coating. A further requirement is that heat sensitive electronic devices require encapsulation with compositions which cure at relatively low temperature.
Presently available silicone resins exhibit some of the properties, but none have the desired combination of strength, flexibility, thermal shock resistance and low temperature cure.
Thus, it is an object of the present invention to provide an improved curable organopolysiloxane composition.
It is another object of the invention to provide an encapsulating resin which is readily cured at low temperatures to form a strong, flexible coating having high thermal shock resistance.
These and other objects of the invention will be apparent to one skilled in the art upon consideration of the following disclosure and appended claims .